nicoga3000 In your case, going through the effort to make some of the Anti-Void weapons is worthwhile, because you don't have the base of 5* Elemental-equipped adventurers to fall back on like a lot of earlier players do. And because you'll be farming for Void Seeds regardless, you'll gain enough materials from that to be able to make a few 5* Void Elementals.
So keep that in mind, the second half of my last post didn't apply to you specifically, but to the player base at large.
Void Zephyr: 5* Elemental Swords dominate this fight, Marth in particular but Naveed/Karl/Euden are fine too. You can get 60 second and faster clears without Dull Res, my best with two randoms and an AI is 51 seconds, but 40 seconds should be possible if first Overdrive is skipped.
Void Agni: 5* Elemental Bow/Wand is perfectly fine, provided at least one player in the room is a non-dead melee with Scorching Res. The melee has an easy enough job that a healer should not be required, and promoted Renee does provide some team healing while still being the #2 melee DPS behind Xander.
Void Poseidon: Hell, 3* and 4* Elementals are fine here on anybody. Go nuts.
Void Jeanne early impressions: 4* and 5* Elementals should be fine, with a preference given to shorter range weapons so that the targeting reticle sticks to Jeanne easier. Yes, inflicting Break makes the fight go faster. No, it isn't required.
None of these fights so far require a healer, though the average player on an average investment level is going to want a healer to prevent themselves from dying.